Typical EGR valves use a simple unbalanced pintle or poppet that is selectively positioned by an actuator relative to a valve seat that circumscribes a passage through the valve housing. Typical actuators are either pneumatic (vacuum) or electric. The actuator receives a control signal, either vacuum, or electric, as the case may be, from a control source and positions the pintle or poppet correspondingly. Sometimes an electric vacuum regulator is used to convert an electrical control signal into a corresponding vacuum control signal for the actuator.
Increasingly stringent demands on the performance of EGR valves in internal combustion engines of automotive vehicles require improved control of the EGR valve, especially during transient operating conditions where engine load and speed change relatively quickly. In order to meet more stringent demands, an electric actuator appears to be a preferred operator for an EGR valve.
An electric actuator, such as a solenoid, can deliver sufficiently fast response, but typically with only comparatively small force over comparatively small travel distances unless the solenoid's size is significantly increased. In this usage, space is usually at a premium, and cost is always a major consideration.
In order to provide an improved EGR valve that can meet more stringent demands through the use of an electric actuator, such as a solenoid, without significantly enlargement of a solenoid actuator, the present invention proposes that the valve be pressure-balanced at least to some significant degree. It is therefore toward a new and improved EGR valve that comprises both an electric actuator and a pressure-balanced valve that the present invention is directed.
Generally speaking, the present invention relates in one aspect to an EGR valve having a pintle that is disposed within an internal passage of the valve housing. This passage extends internally of the housing from an exhaust inlet of the housing to an exhaust outlet of the housing. The pintle is selectively linearly positionable within the housing by means of a linear electric actuator that positions the pintle linearly in correspondence with an electric control signal applied to the actuator. The pintle has opposite axial ends from one of which a shaft extends to operative connection with the electric actuator. The other of these axial ends of the pintle is in communication with the exhaust inlet via the internal passage, and the housing is further constructed to comprises means to communicate the exhaust inlet to the other axial end of the pintle to provide at least some pressure-balancing of the pintle. The housing still further comprises internal valve seat means disposed within the passage at a location that is axially intermediate the opposite axial ends of the pintle for coaction with an axially intermediate portion of the pintle that lies between the pintle's opposite axial ends. The selective positioning of the pintle by the actuator selectively relatively positions the axially intermediate portion of the pintle in relation to the valve seat means for selectively restricting the flow of recirculated exhaust gas through the valve seat means to the exhaust outlet.
In a disclosed embodiment, the axially intermediate portion of the pintle comprises a frustoconically shaped outer surface that is co-axial with the direction of linear actuation of the pintle. The housing comprises a generally cylindrical side wall that bounds the side of a central cylindrical internal space within which the pintle is co-axially disposed; this space is open at one axial end to form the exhaust inlet, and the space itself forms an initial portion of the internal housing passage extending from the exhaust inlet. The space also serves to communicate the opposite axial ends of the pintle to the exhaust inlet for providing at least some degree of pressure-balancing of the pintle. The seat means are provided at the inner distal ends of short tubular stub pipes that are formed integrally with, and extend through, the aforementioned cylindrical wall that bounds the central internal space within which the pintle is disposed. The tubular stub pipes extend radially inwardly from the aforementioned cylindrical housing wall, and in the disclosed embodiment there are two stub pipes diametrically opposite each other. The radially inner distal ends of the tubular stub pipes lie on an imaginary frustoconical surface that is essentially coaxial with the pintle and that is also essentially congruent with the frustoconical outer surface of the pintle when the pintle is seated on said seat means to close the internal passage through the housing to flow. Accordingly, the inner distal ends of the tubular stub pipes have compound curvatures for mating with similarly congruent zones diametrically opposite each other on the outer frustoconical surface of the pintle when the pintle is closed against them in its retracted position. When the pintle is extended away from its retracted position, its frustoconical outer surface unseats from the inner ends of these tubular stub pipes allowing the exhaust to enter the stub pipes and pass through the aforementioned cylindrical wall and ultimately to the exhaust outlet.
Advantageously, the pintle can be fabricated from a material such as stainless steel while the housing can be fabricated from material like aluminum. The distal ends of the tubular stub pipes are advantageously ceramic-coated to provide ceramic coated seating surfaces against which the pintle makes closing contact.
The foregoing, along with further features, advantages, and benefits of the invention, will be seen in the ensuing description and claims which are accompanied by a drawing. The drawing discloses a presently preferred embodiment according to the best mode contemplated at this time for carrying out the invention.